The present invention relates to the preheating treatment of a ferrite, preferably zinc ferrite, catalyst for use in oxidation reactions, and oxidative dehydrogenation (“OXO-D”) of hydrocarbons, in particular for use in conversion of C1-C9 hydrocarbons, and more particularly, C3-C5 hydrocarbons. Further the invention relates to a composition of the catalyst found after the treatment step. The catalyst can be used for the conversion of butene to butadiene. As used herein, butene refers to both butene-1 and butene-2 molecules, and butadiene refers to 1,3 butadiene molecules.
During the startup of an oxidative dehydrogenation process of hydrocarbons employing traditional zinc ferrite catalyst having nitrate components, nitrogen oxides byproduct (NO and NO2), commonly referred to as NOx, is formed. If left within the reaction system, the NOx can react with butene/butadiene and create explosive nitrated compounds. In the past, traditional zinc ferrite, nitrated catalysts were employed in the OXO-D reactor, heated with air and/or steam and/or methane, and NOx components were released to the atmosphere untreated. Due to environmental concerns, releasing of nitrogen oxides is no longer acceptable without treatment. Due to the cost of equipment for NOx treatment among other reasons, a need exists to produce unsaturated hydrocarbons, in particular butadiene, with minimal to no NOx byproducts formed during the oxidation reaction.
Numerous patents and references exist describing heat treatment of catalysts for various reasons, such as regeneration, removal of coke/minimize fouling in a reaction system, or oxidation of the catalyst prior to use in a reactor, among other reasons. Often, in spite of treating the catalyst for removal of specific groups, the user must also deal with the handling issues of the catalyst and care of the catalyst to preserve its effectiveness (conversion/selectivity/yield or CSY performance), robustness, or thermal stability.
See WO 2011/127505 entitled “Vanadate Catalyst for Auto Exhaust Emissions”; EP 2 321 044 entitled “Silver Catalyst for Formaldehyde Preparation”; U.S. Pat. No. 7,582,272 entitled “A Method of Treating a Catalytic Reactor System Prior to Reactor Servicing”; U.S. Pat. No. 5,716,515 entitled “High Temperature Treatment of Reforming Catalyst With an Inert Gas”; PCT Application No. US 2013/034215 describes low emission OXO-D catalyst for butadiene production having improved controllability, and in situ heat processing.
U.S. Pat. No. 4,083,884 to Purdy describes a calcium oxide modified zinc ferrite oxidative dehydrogenation catalyst and use thereof for the production of butadiene. Calcium oxide is used therein as a modifier for the catalyst to suppress carbonyl compound formation during the butene to butadiene reaction. There is no mention of a nitrate-free catalyst or production of nitrogen oxide byproducts in the reaction.
U.S. Pat. No. 4,083,884 discloses activation of the catalyst in situ in reducing atmospheres at a temperature of about 1000° F. (cf Purdy, Col. 6, lines 24-33). During this process a nitrate based catalyst would release NOx into the OXO-D system. The NOx, or nitrogen oxide byproducts, present safety hazards and thus need to be managed for both safety and environmental reasons.
Thus, in view of the formation of nitrogen oxides with the use of traditional ferrite-based catalyst, it would be preferable to find a catalyst or process for formation of butadiene without the NOx byproducts, yet having acceptable catalyst performance and handling during use.
A need exists for a catalyst which can perform at acceptable levels, be sufficiently robust for ease in handling, and also not produce harmful effects to the desired butadiene product or the environment.